More police reduces crime but little is known about the mechanism. Does more police deter crime by reducing its attractiveness, or is the reduction driven by an incapacitation of recurrent criminals?

This paper exploits micro-level data on single robberies together with redeployments of two police forces within a city, providing first evidence of (negative) incapacitation that is driven by reduced clearance rates. During shift turnovers, disrupted patrolling lowers the likelihood of arresting robbers, including repeat offenders, from 13.5 to 8 percent. Offenders do not seem to exploit these inefficiencies.